When two objects interact, what can you say about the forces they exert?
They are equal and opposite
What effect will alcohol and other drugs have on braking distance?
They will only affect thinking distance (which will affect stopping distance)
Name two ways to increase a vehicles top speed
- Reduce air resistance (by making it aerodynamic)
- Increase its power (to increase the thrust driving it forward)
At which stage of this graph is the object travelling at it's terminal velocity?
- c) or e)
- c is terminal velocity before opening the parachute, e) is after opening it
When an object is travelling at its terminal velocity, what do you know about the forces acting on it?
They are balanced (equal and opposite)
What is a resultant force?
A single force that represents the result of adding together several other forces
What is the resultant force in this case?
- The length and direction of the force arrow is important
If the resultant force acting on a stationary object is zero, what will happen to the object?
It will stay stationary
If the resultant force acting on a stationary object is not zero, what will happen to the object?
It will accelerate in the direction of the resultant force
If the resultant force acting on a moving object is zero, what will happen to the object?
It will continue to move at the same speed and in the same direction
If the resultant force acting on a moving object is not zero, what will happen to the object?
The object will accelerate in the direction of the resultant force
What two factors affect the acceleration of an object?
What does the gradient
of a distance-time
What is the speed of the object shown in the first section of this distance-time
- 5 m/s
- (It travels 10 meters in 2 seconds)
What is the difference between speed and velocity?
- Speed just has a size
- Velocity has a size and a direction (a vector)
What does acceleration mean?
How quickly the velocity of an object changes
What does the gradient of a velocity-time graph represent?
How can you calculate distance travelled from a velocity-time graph?
- Calculate the area under the graph
When a vehicle is travelling along a road, which forces resist its movement and which is the biggest?
- Air resistance (biggest)
What is the relationship between
stopping, braking and thinking distances?
- Stopping distance = thinking distance + braking distance
What does thinking distance mean?
The distance you travel whilst your brain is thinking about applying the brakes
Name three things that can affect a driver's thinking distance?
- Alcohol / other drugs
- Distraction (eg on telephone, fiddling with radio)
When vehicle brakes are applied and the vehicle loses kinetic energy, where does the energy go?
Friction between the brakes and the wheel increases the temperature of the brakes
Name three things that can affect a vehicle's braking distance
- Adverse weather conditions (wet or icy)
- Poor condition of vehicle (brakes & tyres only - not whether it is dirty/ rusty/ the winscreen wiper don't work!)
When a body moves through a fluid (liquid or gas), how does speed affect the frictional force on it?
The frictional force (eg air resistance) increases as the speed increases
Why does a parachute reduce a skydiver's terminal velocity?
- When the parachute is open, the air resistance is greater.
- This air resistance will match the weight of the parachutist at a slower speed than if the parachute were not used.
- (At terminal velocity, air resistance = weight)
What is the relationship between weight, mass and the gravitational field strength (g)?
What is the name and symbol for the units of force ?
What is the name and symbol for the unit of mass ?
- Kilogram (kg)
- NOT grammes (g)
When a force changes the shape of an elastic object, in what form is the energy stored inside the object?
Elastic potential energy